Effects of cooling on the thermal accumulation of heat on the development of the fly Lucilia sericata (Meigen) - Preliminary results

The “best practice in forensic entomology” in collecting immature specimens recommends to “store the majority of individuals […] under controlled conditions; cool temperatures are the most suitable (2-6°C). […] The living samples should be transferred to an expert for processing within 24h” (Amendt et al., 2007). This situation is often not possible and sometimes insects can be found later on the corpse after being kept in a cool room for a number of days depending on the public prosecutors discretion. The aim of this work is to investigate the growth and development of different components of the life history of the cosmopolitan necrophagous fly species Lucilia sericata, Meigen (Diptera: Calliphoridae) in a cold environment (refrigeration approximately 4°C). This study will attempt to interpret the effects of this cooling period calculating the time to accumulate thermal units between control and cooled immature stages. The experimental work was conducted at the Centre for Forensic Science (CFS) at University of Western Australia. The experimental work was divided into experimental sessions comprised of different storage conditions of immature stages of small and large masses of larvae with or without food; over long and short period of time either in the fridge or in and out the fridge for different periods of time. The aim of the experimental work was to determine the rate of survival of immature stages in each of the experimental sessions as well as the modification of the rate of growth and any morphological modification of each life history stage. Currently work has been completed for the session concerning the effect of cooling on eggs, larvae and pupae on no substrate. The statistical analyses performed were: descriptive statistics, One Way ANOVA, TUKEY Test, ANOVA with orthogonal contrasts, Logistic Regression. Statistics and Data Analysis tools: Microsoft Excel, JMP. Preliminary results to date: lower temperatures affect the development of L. sericata; concerning survival rate, older stages of the life history of L. sericata are less affected by cooling; eggs just laid cannot survive the thermic stress of cold temperatures. A number of days in the fridge will arrest the development of Lucilia sericata and will be unable to complete its life cycle. Total ADH out of fridge vs refrigerated samples are in general significantly slower to develop than the controls, in particular in all stages prior to reaching the pupal instar. Thermic stress can modify the growth rate but it seems that the overall growth rate itself is not influenced by the amount of thermic stress duration